Popcorn is made by heating popcorn kernels, causing them to explode, as is well known. There are many varieties of corn poppers which are adapted to contain unpopped kernels which may be subjected to heat from any suitable source for the popcorn making process.
In the prior art it has been shown that heat may be applied to the kernels by radiation, convection or conduction in conventional devices, and in the most modern appliances by the application of microwave energy. Conventional devices are, of course, fueled by electrical energy or by the burning of liquid or gaseous fuel.
Popcorn has been made in many ways. Kernels have been placed in a screenlike container with a long handle so that the container may be held suspended above an open flame. Since the heat from the flame usually radiates onto or contacts only one side of the supply of kernels, it is necessary to vigorously shake the container so that all the kernels will be heated and to prevent burning of the popped corn. Another method is to place a supply of kernels in a covered pan disposed on a burner of a kitchen range, for example, and again shake the pan to properly heat all the kernels and agitate the popped corn. Still another method is to place the kernels in an enclosure having wall areas containing electrical heating elements. This method again usually requires that the enclosure be at least slightly agitated. In all of these methods, butter and salt usually must be subsequently added.
It is also known that a partially collapsed sealed foil-like disposable container may be provided with a supply of kernels and oil and agitated over a source of heat whereupon the kernels will pop, causing the container to expand, following which the container may be ruptured to remove the popcorn which will be at least partially covered with the oil. In a still further known method, a partially collapsed, sealed, plastic bag of kernels, with or without oil, is placed in a microwave oven. Microwave radiation is then directed through the oven to the kernels, causing them to pop. Agitation in such a case is not necessary since microwave radiation will easily contact each kernel. A suitable oil may also be provided in this type of device.
It has been found that butter can not be used satisfactorily with the packaged systems because butter can become rancid after a period of time such as might occur when the packages are stored or on store shelves for a lengthy period. Oils which may be used as substitutes for butter usually have a different and sometimes undesirable taste.
An improved corn popping appliance is described in two U.S. patent applications, Ser. No. 865,824, Bowen et al, filed Dec. 30, 1977, and Ser. No. 866,081, Teich et al, filed Dec. 30, 1977, both of which are assigned to the same assignee as the present invention. This appliance is especially adapted to utilize microwave energy as the heat source and preferably comprises a bowl or container of microwave-transparent material which is substantially conical in shape so that kernels may be retained in a clump in the small end of the container. The container is supported with its small end within a comating cavity formed in an encircling microwave concentrator. Upon subjection of the device to microwave radiation, such as in a microwave oven, the kernels will become heated directly by the microwave radiation and by heat generated by the concentrator and, as a consequence, will expand or explode. Such exploding kernels will be propelled upwardly into the wider portion of the container while unpopped kernels will continue to be retained clumped in the small end of the container for eventual popping. In this microwave appliance no means has been disclosed for adding butter to the produced popcorn.